Examination of the Insulin-like Growth Factor System with the Onset of Lactation in Dairy Cows PDF Download

Author: Nthabisheng Segoale
Publisher:
ISBN:
Category :
Languages : en
Pages : 308

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Author: Michelle Lynn Bode-Rhoads
Publisher:
ISBN:
Category : Somatomedin
Languages : en
Pages : 376

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The components of the growth hormone (GH)/insulin-like growth factor (IGF) system play critical reproductive and metabolic roles in dairy cattle. In liver, GH receptor (GHR) and IGF-I are dynamically regulated by lactation and energy balance. Less is known about the regulation of GHR and IGF-I mRNA in reproductive tissues. The objective of these studies was to measure the expression of total GHR (tGHR), IGF-I and IGF binding protein (IGFBP) 2 mRNA in reproductive tissues during several stages of lactation and around the time of artificial insemination. Changes in gene expression were then evaluated for potential effects on fertility. The expression of tGHR, IGF-I and IGFBP-2 was measured in uterine, luteal, follicular and hepatic tissue three times during the early postpartum period. Expression of tGHR and IGFBP-2 mRNA in the reproductive tissues did not change during early lactation. Luteal and follicular expression of IGF-I changed in an inverse manner from the second sample collection to the third (luteal expression decreased and follicular expression increased). Further research is needed to elucidate the implications these changes have for fertility in dairy cattle. The expression of tGHR, IGF-I and IGFBP-2 was also measured in uterine and hepatic tissue at several stages of lactation around the time of insemination. Uterine tGHR mRNA, uterine IGF-I mRNA and plasma IGF-I concentrations increased at estrus. The timing of these changes suggests that uterine IGF-I does not directly affect early embryonic development, but may enhance the uterine environment for early embryonic development. The cows that became pregnant had higher liver tGHR and IGFBP-2 mRNA concentrations. The cows that became pregnant may have been metabolically distinct from the cows that did not become pregnant, resulting in different levels of hepatic gene expression and providing a reproductive advantage.

Author: Mark A. McGuire
Publisher:
ISBN:
Category :
Languages : en
Pages : 392

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Author: Wendie Smith Cohick
Publisher:
ISBN:
Category : Bovine somatotropin
Languages : en
Pages : 354

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Author: Monica Reynolds
Publisher: University of Pennsylvania Press
ISBN: 1512806056
Category : Medical
Languages : en
Pages : 284

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Proceedings of a symposium, satellite to the 24th International Congress of Physiological Sciences, University of Pennsylvania.

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309037956
Category : Medical
Languages : en
Pages : 384

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This lively book examines recent trends in animal product consumption and diet; reviews industry efforts, policies, and programs aimed at improving the nutritional attributes of animal products; and offers suggestions for further research. In addition, the volume reviews dietary and health recommendations from major health organizations and notes specific target levels for nutrients.

Author: Robert Paul Rhoads
Publisher:
ISBN: 9780496620098
Category :
Languages : en
Pages : 193

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In transition dairy cows, plasma insulin-like growth factor (IGF)-I declines near parturition despite elevated growth hormone (GH). Furthermore, GH administration cannot restore plasma IGF-I suggesting impaired hepatic GH-dependent IGF-I production. In contrast, the metabolic effects of GH on adipose tissue are believed to persist. Objectives of this thesis were: (1) To determine the role of insulin in the regulation of hepatic IGF-I production during early lactation and (2) To examine the GH responsiveness of liver and adipose tissue during undernutrition. The first study showed that hepatic cyclophilin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA abundance was regulated during the transition period, periods of hyperinsulinemia and poor nutrition. In the second study, a reduction in plasma insulin paralleled exactly the deteriorating energy balance during the periparturient period. To test the role of insulin, we performed hyperinsulinemic-euglycemic clamps in late pregnant and early lactating dairy cows. Hyperinsulinemia increased plasma IGF-I irrespective of physiological state. This effect was associated with increased abundance of hepatic IGF-I mRNA. Furthermore, insulin increased hepatic GH receptor (GHR) abundance by stimulating GHR1A mRNA. Finally, insulin increased the abundance of the GHR in adipose tissue without altering total GHR mRNA indicating that the regulation of GHR synthesis differs between tissues. In the third study, late lactating dairy cows were treated for 4 days with saline or bovine somatotropin (bST) when well-fed (120% of total requirements) or underfed (30% of maintenance requirements). Underfed cows approximated early lactating cows in their degree of negative energy balance, elevations in plasma GH and reductions in plasma IGF-I and insulin. Underfed cows had decreased GHR abundance in liver and adipose tissue without a reduction in GHR mRNA. In well-fed cows, both tissues responded in a robust manner to GH (parameters were plasma IGF-I concentration for liver, epinephrine-stimulated plasma NEFA for adipose tissue, and IGF-I mRNA for both tissues). In underfed cows, these responses were reduced in liver and lost completely in adipose tissue. In conclusion, an adequate level of insulin is needed for hepatic IGF-I production. Lower GHR abundance cannot completely account for reduced GH responsiveness of liver and adipose tissue in underfed cows.

Author: Jean A. Larson
Publisher:
ISBN:
Category : Bovine somatotropin
Languages : en
Pages : 110

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Author: Harald Volden
Publisher: Springer Science & Business Media
ISBN: 9086867189
Category : Science
Languages : en
Pages : 172

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NorFor is a semi-mechanistic feed evaluation system for cattle, which is used by advisors in Denmark, Iceland, Norway and Sweden. This book describes in detail the system and it covers five main sections. The first is concerned with information on feed characteristics, feed analysis and feed digestion methods. The second section describes the digestion and metabolism in the gastrointestinal tract and the supply and requirement of energy and metabolizable amino acids. The third section considers the prediction of feed intake and physical structure of the diet. The fourth section focuses on model evaluation and the final section provides information on the IT solutions and feed ration formulation by a non-linear economical optimization procedure. This book will be of significant interest to researchers, students and advisors of cattle nutrition and feed evaluation.

Author: Laurie Ann Winkelman
Publisher:
ISBN:
Category : Animal nutrition
Languages : en
Pages : 238

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Abstract: The somatotropic axis is a critical endocrine system for partitioning nutrients toward lactation during the transition period. Growth hormone receptor (GHR) 1A is down regulated in the liver of the dairy cow after calving, causing an uncoupling of the somatotropic axis that leads to increased plasma growth hormone (GH) and reduced circulating insulin-like growth factor-I (IGF-I). Other mechanisms responsible for uncoupling the somatotropic axis have not been examined in the liver of transition dairy cows. This includes the presence of suppressors of cytokine signaling (SOCS) that inhibit post-receptor signaling. The objective of this study was to influence components of the somatotropic axis and its signaling cascade to improve IGF-I and insulin status of transition dairy cows through a diet designed to improve postpartum energy balance (EB). Approximately 45 days before expected calving date, multiparous Holstein cows were dried off and fed either a restricted (R, 9.4 kg DM/d; n 9) or ad libitum (AL, n = 9) diet that was balanced for energy requirements. The R diet was designed for the cows to maintain a more stable DMI and EB before calving. After calving, all cows were fed the same lactation ration. Blood samples were collected weekly beginning at dry-off, with more intensive sampling near parturition, and sampling continued until day 28 after calving. Liver biopsies were collected on days -21, -7, 2, and 28 relative to calving. Prepartum dietary treatment had no effect on postpartum dry matter intake (DMI) or EB. Plasma glucose, non-esterified fatty acids (NEFA), insulin, and IGF-I were not affected by dietary treatment either before or after calving, but there was an interaction between treatment and time for postpartum EB and plasma IGF-I. The R cows had higher plasma IGF-I concentrations on days 4 and 7 of lactation, coinciding with higher EB on days 2, 4 and 6. Relative steady state concentrations of SOCS-2 mRNA increased on day 2 of lactation for all cows and the increase was greater for R than AL cows. Changes in SOCS-2 mRNA coincided with increased plasma concentrations of estradiol-17[beta] near parturition. Liver GHR 1A mRNA relative abundance tended to decrease by 70 percent between day -7 and +2 relative to calving. We conclude that SOCS-2 is expressed in dairy cow liver and SOCS-2 mRNA expression is upregulated after calving. Liver SOCS-2 and reduced GHR 1A may work together after parturition, causing uncoupling of the somatotropic axis. The relationship between EB, SOCS-2, and GH signaling warrants further investigation.